Field of the Invention
The present invention relates to an image forming apparatus including a belt member to be driven.
Description of the Related Art
There has been widely used an image forming apparatus including a belt conveying device in which a belt member to be driven by a driving roller is steered by a steering roller. An example of a belt conveying device is an intermediate transfer belt on which a toner image born on an image-bearing member is transferred at a primary transfer portion and which conveys the toner image to a secondary transfer portion to transfer the toner image onto a recording medium.
Various steering methods for the belt conveying device have been put to practical use.
Japanese Patent Laid-Open No. 9-169449 describes a belt conveying device of a forced steering type in which the lateral position of a belt member is detected with a sensor and a steering roller is tilted by operating an actuator and a motor. Japanese Patent Laid-Open No. 2001-146335 describes a belt conveying device of a steering type in which a steering roller biased at both ends by spring members tilts in an abutting direction according to the lateral position of a belt member.
PCT Japanese Translation Patent Publication No. 2001-520611 describes a belt conveying device of an autonomous steering type in which a steering roller turnably supported at a center portion in the rotation axis direction autonomously tilts according to the torque balance of the frictional force corresponding to the lateral position of a belt member.